Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and an image processing program for performing a weighting addition process with respect to two radiation images.
Related Art
In the related art, a variety of diagnosis has been performed using a radiation image. In this regard, a radiation image addition process of reducing quantum noise (hereinafter, referred to as noise) of radiation included in a radiation image has been proposed to enhance diagnosis performance. The addition process is performed by acquiring a radiation image from each detection means such as a plurality of radiation detectors that are disposed in an overlapping manner and adding the plurality of radiation images between corresponding pixels. By performing such an addition process, it is possible to acquire a high-quality addition image with the S/N ratio in which noise is reduced.
Further, in the addition process, a variety of techniques for acquiring a processed image with high quality have been proposed. For example, JP1995-159910A (JP-H07-159910A) has proposed a technique for changing addition rates of two radiation images according to the amount of radiation in imaging, the kind of detection means, a frequency to be focused in a radiation image, and the like to generate an addition image in which the S/N ratio becomes a maximum. Further, JP1995-287330A (JP-H07-287330A) has proposed a technique for calculating a mask filter having a frequency characteristic for enhancing the S/N ratio of an addition image on the basis of the amount of radiation, and performing convolution with respect to each radiation image using the mask filter to obtain an addition image. Furthermore, JP1995-319092A (JP-H07-319092A) has proposed a technique for resolving frequencies of two radiation images to be added, performing addition using different addition rates for each frequency band, and performing demultiplexing resolution conversion with respect to the addition image for each frequency band to obtain an addition image.
In order to achieve two radiation images for performing the above-mentioned addition process, a two-shot method in which imaging is performed two times, and a one-shot method in which two detection means that are disposed in an overlapping manner are simultaneously irradiated with radiation that passes through a subject so that the two radiation images are simultaneously acquired are known.